Nanoparticulate compositions of immunosuppressive agents

ABSTRACT

There is disclosed an aerosol comprising droplets of an aqueous dispersion of nanoparticles, said nanoparticles comprising insoluble therapeutic or diagnostic agent particles having a surface modifier on the surface thereof. There is also disclosed a method for making the aerosol and methods for treatment and diagnosis using the aerosol.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.08/394,103, filed on Feb. 24, 1995.

FIELD OF THE INVENTION

The present invention is directed to the field of nanoparticles andparticularly in an aerosol form.

BACKGROUND OF THE INVENTION

Delivery of therapeutic agent to the respiratory tract is important forboth local and systemic treatment of disease. With the conventionaltechniques, delivery of agents to the lung is extremely inefficient.Attempts to develop respirable aqueous suspensions of poorly solublecompounds have been unsuccessful. Micronized therapeutic agentssuspended in aqueous media are too large to be delivered by aerosolizedaqueous droplets. With conventional processes, it is estimated that onlyabout 10 to 20% of the agent reaches the lung. Specifically, there isloss to the device used to deliver the agent, loss to the mouth andthroat and with exhalation. These losses lead to variability intherapeutic agent levels and poor therapeutic control. In addition,deposition of the agent to the mouth and throat can lead to systemicabsorption and undesirable side effects.

The efficiency of respiratory drug delivery is largely determined by theparticle size distribution. Large particles (greater than 10 m) areprimarily deposited on the back of the throat. Greater than 60% of theparticles with sizes between 1 and 10 m pass with the air stream intothe upper bronchial region of the lung where most are deposited. Withparticles less than about 1 μm, essentially all of the particles enterthe lungs and pass into the peripheral alveolar region; however, about70% are exhaled and therefore are lost.

In addition to deposition, the relative rate of absorption and rate ofclearance of the therapeutic agent must be considered for determiningthe amount of therapeutic agent that reaches the site of action. Since99.99% of the available area is located in the peripheral alveoli, rapidabsorption can be realized with delivery of the particles to theperiphery. For clearance, there is also differences between the centraland peripheral regions of the lung. The peripheral alveolar regiondoes-not have ciliated cells but relies on macrophage engulfment forparticle clearance. This much slower process can significantly extendthe time during which the particles reside in the lung thereby enhancingthe therapeutic or diagnostic effect. In contrast, particles depositedin the upper respiratory tract are rapidly cleared by mucociliaryescalator. That is, the particles are trapped in the mucous blanketcoating the lung surface and are transported to the throat. Hence, thismaterial is either swallowed or removed by coughing.

While it has long been known that smaller droplets of an aerosol reachdeeper into the respiratory system (Current Concepts in thePharmaceutical Sciences: Dosage and Bioavailability, J. Swarbrick Ed.,Lea and Febiger, Philadelphia, Pa., 1973, pp. 97-148) these have largelybeen of theoretical interest. Simply knowing that smaller droplets ofaerosol can be delivered deeper into the respiratory system does notsolve the problem of incorporating sufficient therapeutic agent into theaerosol to be efficient, particularly where the therapeutic agent isonly slightly soluble in the liquid for the aerosol.

Nanoparticles, described in U.S. Pat. No. 5,145,684, are particlesconsisting of a poorly soluble therapeutic or diagnostic agent ontowhich are adsorbed a non-crosslinked surface modifier, and which have anaverage particle size of less than about 400 nanometers (nm). However,no mention is made of attempts to nebulize (aerosolize or atomize areequivalent terms for the purpose of this disclosure) these compositionsand it is not apparent that nebulizing these composition would provideuseful aerosols or that there would be any advantage for doing so.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided an aerosolcomprising droplets of an aqueous dispersion of nanoparticles, saidnanoparticles comprising insoluble therapeutic or diagnostic agentparticles having a surface modifier on the surface thereof.

In another aspect of the invention, there is provided a method forforming an aerosol of a nanoparticle dispersion, said nanoparticlescomprising insoluble therapeutic or diagnostic agent particles having asurface modifier on the surface thereof, said method comprising thesteps of:

a) providing a suspension of said nanoparticles;

b) nebulizing said suspension so as to form an aerosol.

In yet another aspect of the invention, there is provided a method oftreating a mammal comprising the steps of:

a) forming an aerosol of an aqueous dispersion of nanoparticles, saidnanoparticles comprising insoluble therapeutic agent particles having asurface modifier on the surface thereof;

b) administering said aerosol to the respiratory system of said mammal.

In yet another embodiment, there is provided a method of diagnosing amammal, said method comprising

a) forming an aerosol of an aqueous dispersion of nanoparticles, saidnanoparticles comprising insoluble diagnostic imaging agent particleshaving a surface modifier on the surface thereof;

b) administering said aerosol to the respiratory system of said mammal;and

c) imaging said imaging agent in said respiratory system.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of the invention are aerosols. Aerosols can be definedfor the present purpose as colloidal systems consisting of-very finelydivided liquid droplets dispersed in and surrounded by a gas. Thedroplets in the aerosols typically have a size less than about 50microns in diameter although droplets of a much smaller size arepossible.

The aerosols of the present invention are particularly useful in thetreatment of respiratory related illnesses such as asthma, emphysema,respiratory distress syndrome, chronic bronchitis, cystic fibrosis andacquired immune deficiency syndrome including AIDS related pneumonia.

The aerosols of the invention are made by nebulizing the nanoparticlecontaining solution using a variety of known nebulizing techniques.Perhaps the simplest of systems is the “wo-phase” system which consistsof a solution or a suspension of active ingredient, in the present case,a nanoparticle containing a therapeutic or diagnostic agent, in a liquidpropellent. Both liquid and vapor phases are present in a pressurizedcontainer and when a valve on the container is opened, liquid propellentcontaining the nanoparticle dispersion is released. Depending on thenature of the ingredients and the nature of the valve mechanism, a fineaerosol mist or aerosol wet spray is produced.

There are a variety of nebulisers that are available to produce theaerosols of the invention including small volume nebulizers. Compressordriven nebulizers incorporate jet technology and use compressed air togenerate the aerosol. Commercially available devices are available fromHealthdyne Technologies Inc; Invacare Inc.; Mountain Medical EquipmentInc.; Pari Respiratory Inc.; Mada Mediacal Inc.; Puritan-Bennet; SchucoInc.; Omron Healthcare Inc.; DeVilbiss Health Care Inc; and HospitakInc.

Ultrasonic nebulizers deliver high medication output and are used bypatients-suffering from severe asthma, or other severe respiratoryrelated illnesses.

The particles comprise a therapeutic or diagnostic agent. (therapeuticagents are sometimes referred to as drugs or pharmaceuticals. Thediagnostic agent referred to is typically a contrast agent such as anx-ray contrast agent but can also be other diagnostic materials.) Thetherapeutic or diagnostic agent exists as a discrete, crystalline phase.The crystalline phase differs from a non-crystalline or amorphous phasewhich results from precipitation techniques, such as described in EPO275,796.

The invention can be practiced with a wide variety of therapeutic ordiagnostic agents. The therapeutic or diagnostic agent preferably ispresent in an essentially pure form. The therapeutic or diagnostic agentmust be poorly soluble and dispersible in at least one liquid medium. By“poorly soluble” it is meant that the therapeutic or diagnostic agenthas a solubility in the liquid dispersion medium of less than about 10mg/mL, and preferably of less than about 1 mg/mL. A preferred liquiddispersion medium is water. However, the invention can be practiced withother liquid media in which a therapeutic or diagnostic agent is poorlysoluble and dispersible including, for example, aqueous salt solutions,safflower oil and solvents such as ethanol, t-butanol, hexane andglycol. The pH of the aqueous dispersion media can be adjusted bytechniques known in the art.

Suitable therapeutic or diagnostic agents can be selected from a varietyof known classes of therapeutic or diagnostic agents including, forexample, analgesics, anti-inflammatory agents, anthelmintics,anti-arrhythmic agents, antibiotics (including penicillins),anticoagulants, antidepressants, antidiabetic agents, antiepileptics,antihistamines, antihypertensive agents, antimuscarinic agents,antimycobacterial agents, antineoplastic agents, immunosuppressants,antithyroid agents, antiviral agents, anxiolytic sedatives (hypnoticsand neuroleptics), astringents, beta-adrenoceptor blocking agents, bloodproducts and substitutes, cardiac inotropic agents, contrast media,corticosteroids, cough suppressants (expectorants and mucolytics),diagnostic agents, diagnostic imaging agents, diuretics, dopaminergics(antiparkinsonian agents), haemostatics, immunological agents, lipidregulating agents, muscle relaxants, parasympathomimetics, parathyroidcalcitonin and biphosphonates, prostaglandins, radio-pharmaceuticals,sex hormones (including steroids), anti-allergic agents, stimulants andanoretics, sympathomimetics, thyroid agents, vasodilators and xanthines.Preferred therapeutic or diagnostic agents include those intended fororal administration and intravenous administration. A description ofthese classes of therapeutic agents and diagnostic agents and a listingof species within each class can be found in Martindale, The ExtraPharmacopoeia, Twenty-ninth Edition, The Pharmaceutical Press, London,1989. The therapeutic or diagnostic agents are commercially availableand/or can be prepared by techniques known in the art.

Preferred diagnostic agents include the x-ray imaging agent WIN-8883(ethyl 3,5-diacetamido-2,4,6triiodobenzoate) also known as the ethylester of diatrazoic acid (EEDA), WIN 67722, i.e.,(6-ethoxy-6-oxohexyl-3,5-bis(acetamido)-2,4,6-triiodobenzoate;ethyl-2-(3,5-bis(acetamido)-2,4,6-triiodobenzoyloxy)butyrate (WIN16318); ethyl diatrizoxyacetate (WIN 12901); ethyl2-(3,5bis(acetamido)-2,4,6-triiodobenzoyloxy)propionate (WIN 16923);N-ethyl 2-(3,5-bis(acetamido)-2,4,6triiodobenzoyloxy acetamide (WIN65312); isopropyl 2(3,5-bis(acetamido)-2,4,6-triiodobenzoyloxy)acetamide(WIN 12855); diethyl 2-(3,5-bis(acetamido)-2,4,6triiodobenzoyloxymalonate (WIN 67721); ethyl2-(3,5bis(acetamido)-2,4,6-triiodobenzoyloxy)phenylacetate (WIN 67585);propanedioic acid,[[3,5-bis(acetylamino)2,4,5-triodobenzoyl]oxy]-,bis(1-methyl)ester (WIN68165); and benzoic acid, 3,5-bis(acetylamino)-2,4,6triodo-,4-(ethyl-3-ethoxy-2-butenoate) ester (WIN 68209). Suitable diagnosticagents are also disclosed in U.S. Pat. No. 5,260,478; U.S. Pat. No.5,264,610; U.S. Pat. No. 5,322,679 and U.S. Pat. No. 5,300,739.

Preferred contrast agents include those which are expected todisintegrate relatively rapidly under physiological conditions, thusminimizing any particle associated inflammatory response. Disintegrationmay result from enzymatic hydrolysis, solubilization of carboxylic acidsat physiological pH, or other mechanisms. Thus, poorly soluble iodinatedcarboxylic acids such as iodipamide, diatrizoic acid, and metrizoicacid, along with hydrolytically labile iodinated species such as WIN67721, WIN 12901, WIN 68165, and WIN 68209 or others may be preferred.

Surface Modifiers

Suitable surface modifiers can preferably be selected from known organicand inorganic pharmaceutical excipients. Such excipients include variouspolymers, low molecular weight oligomers, natural products andsurfactants. Preferred surface modifiers include nonionic and ionicsurfactants.

Representative examples of surface modifiers include gelatin, casein,lecithin (phosphatides), gum acacia, cholesterol, tragacanth, stearicacid, benzalkonium chloride, calcium stearate, glycerol monostearate,cetostearyl alcohol, cetomacrogol emulsifying wax, sorbitan esters,polyoxyethylene alkyl ethers, e.g., macrogol ethers such as cetomacrogol1000, polyoxyethylene castor oil derivatives, polyoxyethylene sorbitanfatty acid esters, e.g., the commercially available Tweens™,polyethylene glycols, polyoxyethylene stearates, colloidal silicondioxide, phosphates, sodium dodecylsulfate, carboxymethylcellulosecalcium, carboxymethylcellulose sodium, methylcellulose,hydroxyethylcellulose, hydroxy propylcellulose,hydroxypropylmethylcellulose phthalate, noncrystalline cellulose,magnesium aluminum silicate, triethanolamine, polyvinyl alcohol, andpolyvinylpyrrolidone (PVP). Most of these surface modifiers are knownpharmaceutical excipients and are described in detail in the Handbook ofPharmaceutical Excipients, published jointly by the AmericanPharmaceutical Association and The Pharmaceutical Society of GreatBritain, the Pharmaceutical Press, 1986.

Particularly preferred surface modifiers include polyvinylpyrrolidone,tyloxapol, poloxamers such as Pluronics™ F68 and F108, which are blockcopolymers of ethylene oxide and propylene oxide, and polyxamines suchas Tetronics™ 908 (also known as Poloxamine™ 908), which is atetrafunctional block copolymer derived from sequential addition ofpropylene oxide and ethylene oxide to ethylenediamine, available fromBASF, dextran, lecithin, dialkylesters of sodium sulfosuccinic acid,such as Aerosol OTs™, which is a dioctyl ester of sodium sulfosuccinicacid, available from American Cyanimid, Duponols™ P, which is a sodiumlauryl sulfate, available from DuPont, Tritons™ X-200, which is an alkylaryl polyether sulfonate, available from Rohn and Haas, Tween™ 20 andTweens™ 80, which are polyoxyethylene sorbitan fatty acid esters,available from ICI Specialty Chemicals; Carbowaxs™ 3550 and 934, whichare polyethylene glycols available from Union Carbide; Crodestas™ F-110,which is a mixture of sucrose stearate and sucrose distearate, availablefrom Croda Inc., Crodestas™ SL-40, which is available from Croda, Inc.,and SA9OHCO, which is C₁₈H₃₇CH₂(CON(CH₃)CH₂(CHOH)₄(CH₂OH)₂. Surfacemodifiers which have been found to be particularly useful includeTetronics™ 908, the Tweenss™, Pluronics™ F-68 and polyvinylpyrrolidone.Other useful surface modifiers 15 include:

decanoyl-N-methylglucamide;

n-decyl β-D-glucopyranoside;

n-decyl β-D-maltopyranoside;

n-dodecyl β-D-glucopyranoside;

n-dodecyl β-D-maltoside;

heptanoyl-N-methylglucamide;

n-heptyl-β-D-glucopyranoside;

n-heptyl β-D-thioglucoside; n-hexyl β-D-glucopyranoside;

nonanoyl-N-methylglucamide;

n-noyl β-D-glucopyranoside;

octanoyl-N-methylglucamide;

n-octyl-βD-glucopyranoside;

octyl β-D-thioglucopyranoside; and the like.

Another useful surface modifier is tyloxapol (a nonionic liquid polymerof the alkyl aryl polyether alcohol type; also known as superinone ortriton). This surface modifier is commercially available and/or can beprepared by techniques known in the art.

Another preferred surface modifier is p-isononylphenoxypoly(glycidol)also known as. Olin-IOG™ or Surfactant 10-G, is commercially availableas IOG™ from Olin Chemicals, Stamford, Conn.

Non-Ionic Surface Modifiers

Preferred surface modifiers can be selected from known non-ionicsurfactants, including the poloxamines such as Tetronic™ 908 (also knownas Poloxamine™ 908), which is a tetrafunctional block copolymer derivedfrom sequential addition of propylene oxide and ethylene oxide toethylenediamine, available from BASF, or Tetronic™ 1508 (T-1508), or apolymer of the alkyl aryl polyether alcohol type, such as tyloxapol.

The surface modifiers are commercially available and/or can be preparedby techniques known in the art. Two-or more surface modifiers can beused in combination.

Tyloxapol

Tyloxapol (4-(1,1,3,3-tetramethylbutyl)-phenol polymer with ethyleneoxide and formaldehyde) is a preferred surface modifier and is anonionic liquid polymer of the alkyl aryl polyether alcohol type.Tyloxapol, also known as “Superinone”, is disclosed as useful as anonionic surface active agent in a lung surfactant composition in U.S.Pat. No. 4,826,821 and as a stabilizing agent for 2-dimethylaminoethyl4-n-butylaminobenzoate in U.S. Pat. No. 3,272,700.

Tyloxapol may be associated with the nanoparticles and may function as asurface modifier, as a stabilizer, and/or as a dispersant.Alternatively, the tyloxapol may serve other purposes. Tyloxapol mayserve all three functions. The tyloxapol may serve as a stabilizerand/or a dispersant, whereas another compound acts as a surfacemodifier.

Auxiliary Surface Modifiers

Particularly preferred auxiliary surface modifiers are those whichimpart resistance to particle aggregation during sterilization andinclude dioctylsulfosuccinate (DOSS), polyethylene glycol, glycerol,sodium dodecyl sulfate, dodecyl trimethyl ammonium bromide and a chargedphospholipid such as dimyristoyl phophatidyl glycerol. The surfacemodifiers are commercially available and/or can be prepared bytechniques known in the art. Two or more surface modifiers can be usedin combination.

Block Copolymer Surface Modifiers

One preferred surface modifier is a block copolymer linked to at leastone anionic group. The polymers contain at least one, and preferablytwo, three, four or more anionic groups per molecule.

Preferred anionic groups include sulfate, sulfonate, phosphonate,phosphate and carboxylate groups. The anionic groups are covalentlyattached to the nonionic block copolymer. The nonionic sulfatedpolymeric surfactant has a molecular weight of 1,000-50,000, preferably2,000-40,000 and more preferably 3,000-30,000. In preferred embodiments,the polymer comprises at least about 50%, and more preferably, at leastabout 60% by weight of hydrophilic units, e.g., alkylene oxide units.The reason for this is that the presence of a major weight proportion ofhydrophilic units confers aqueous solubility to the polymer.

A preferred class of block copolymers useful as surface modifiers hereinincludes sulfated block copolymers of ethylene oxide and propyleneoxide. These block copolymers in an unsulfated form are commerciallyavailable as Pluronics™. Specific examples of the unsulfated blockcopolymers include F68, F108 and F127.

Another preferred class of block copolymers useful herein includetetrafunctional block copolymers derived from sequential addition ofethylene oxide and propylene oxide to ethylene diamine. These polymers,in an unsulfated form, are commercially available as Tetronics™.

Another preferred class of surface modifiers contain at least onepolyethylene oxide (PEO) block as the hydrophilic portion of themolecule and at least one polybutylene oxide (PBO) block as thehydrophobic portion. Particularly preferred surface modifiers of thisclass are diblock, triblock, and higher block copolymers of ethyleneoxide and butylene oxide, such as are represented, for example, by thefollowing structural formula:

The block copolymers useful herein are known compounds and/or can bereadily prepared by techniques well known in the art.

Highly preferred surface modifiers include triblock copolymers of thePEOPBOPEO having molecular weights of 3800 and 5000 which arecommercially available from Dow Chemical, Midland, Mich., and arereferred to as B20-3800 and B20-5000. These surface modifiers containabout 80% by weight PEO. In a preferred embodiment, the surface modifieris a triblock polymer having the structure:

Q is an anionic groupwherein

R is H or a metal cation such as Na+, K+ and the like,

x is 15-700,

Y is 5-200 and

z is 15-700. 30

Grinding

The described particles can be prepared in a method comprising the stepsof dispersing a therapeutic or diagnostic agent in a liquid dispersionmedium and applying mechanical means in the presence of grinding mediato reduce the particle size of the therapeutic or diagnostic agent to aneffective average particle size of less than about 400 nm. The particlescan be reduced in size in the presence of a surface modifier.Alternatively, the particles can be contacted with a surface modifierafter attrition.

The therapeutic or diagnostic agent selected is obtained commerciallyand/or prepared by techniques known in the art in a conventional coarseform. It is preferred, but not essential, that the particle size of thecoarse therapeutic or diagnostic agent selected be less than about 10 mmas determined by sieve analysis. If the coarse particle size of thetherapeutic or diagnostic agent is greater than about 100 mm, then it ispreferred that the particles of the therapeutic or diagnostic agent bereduced in size to less than 100 mm using a conventional milling methodsuch as airjet or fragmentation milling.

The coarse therapeutic or diagnostic agent selected can then be added toa liquid medium in which it is essentially insoluble to form a premix.The concentration of the therapeutic or diagnostic agent in the liquidmedium can vary from about 0.1-60%, and preferably is from 5-30% (w/w).It is preferred, but not essential, that the surface modifier be presentin the premix. The concentration of the surface modifier can vary fromabout 0.1 to about 90%, and preferably is 1-75%, more preferably 20-60%,by weight based on the total combined weight of the therapeutic ordiagnostic agent and surface modifier. The apparent viscosity of thepremix suspension is preferably less than about 1000 centipoise.

The premix can be used directly by subjecting it to mechanical means toreduce the average particle size in the dispersion to less than 1000 nm.It is preferred that the premix be used directly when a ball mill isused for attrition. Alternatively, the therapeutic or diagnostic agentand, optionally, the surface modifier, can be dispersed in the liquidmedium using suitable agitation, e.g., a roller mill or a Cowles typemixer, until a homogeneous dispersion is observed in which there are nolarge agglomerates-visible to the naked eye. It is preferred that thepremix be subjected to such a premilling dispersion step when arecirculating media mill is used for attrition. Alternatively, thetherapeutic or diagnostic agnet and, optionally, the surface modifier,can be dispersed in the liquid medium using suitable agitation, e.g., aroller mill or a Cowles type mixer, until a homogeneous dispersion isobserved in which there are no large agglomerates visible to the nakedeye. It is preferred that the premix be subjected to such a premillingdispersion step when a recirculating media mill is used for attrition.

The mechanical means applied to reduce the particle size of thetherapeutic or diagnostic agent conveniently can take the form of adispersion mill. Suitable dispersion mills include a ball mill, anattritor mill, a vibratory mill, and media mills such as a sand mill anda bead mill. A media mill is preferred due to the relatively shortermilling time required to provide the intended result, desired reductionin particle size. For media milling, the apparent viscosity of thepremix preferably is from about 100 to about 1000 centipoise. For ballmilling, the apparent viscosity of the premix preferably is from about 1up to about 100 centipoise. Such ranges tend to afford an optimalbalance between efficient particle fragmentation and media erosion.

Preparation Conditions

The attrition time can vary widely and depends primarily upon theparticular mechanical means and processing conditions selected. For ballmills, processing times of up to five days or longer may be required. Onthe other hand, processing times of less than 1 day (residence times ofone minute up to several hours) have provided the desired results usinga high shear media mill.

The particles must be reduced in size at a temperature which does notsignificantly degrade the therapeutic or diagnostic agent. Processingtemperatures of less than about 30-40 C are ordinarily preferred. Ifdesired, the processing equipment can be cooled with conventionalcooling equipment. The method is conveniently carried out underconditions of ambient temperature and at processing pressures which aresafe and effective for the milling process. For example, ambientprocessing pressures are typical of ball mills, attritor mills andvibratory mills. Control of the temperature, e.g., by jacketing orimmersion of the milling chamber in ice water are contemplated.Processing pressures from about 1 psi (0.07 kg/cm2) up to about 50 psi(3.5 kg/cm2) are contemplated. Processing pressures from about 10 psi(0.7 kg/cm2) to about 20 psi 1.4 kg/cm2)

The surface modifier, if it was not present in the premix, must be addedto the dispersion after attrition in an amount as described for thepremix above. Thereafter, the dispersion can be mixed, e.g., by shakingvigorously. Optionally, the dispersion can be subjected to a sonicationstep, e.g., using an ultrasonic power supply. For example, thedispersion can be subjected to ultrasonic energy having a frequency of20-80 kHz for a time of about 1 to 120 seconds.

After attrition is completed, the grinding media is separated from themilled particulate product (in either a dry or liquid dispersion form)using conventional separation techniques, such as by filtration, sievingthrough a mesh screen, and the like.

Grinding Media

The grinding media for the particle size reduction step can be selectedfrom rigid media preferably spherical or particulate in form having anaverage size less than about 3 mm and, more preferably, less than about1 mm. Such media desirably can provide the particles with shorterprocessing times and impart less wear to the milling equipment. Theselection of material for the grinding media is not believed to becritical. We have found that zirconium oxide, such as 95% ZrO2stabilized with magnesia, zirconium silicate, and glass grinding mediaprovide particles having levels of contamination which are believed tobe acceptable for the preparation of pharmaceutical compositions.However, other media, such as stainless steel, titania, alumina, and 95%ZrO2 stabilized with yttrium, are expected to be useful. Preferred mediahave a density greater than about 3 g/cm3.

Polymeric Grinding Media

The grinding media can comprise particles, preferably substantiallyspherical in shape, e.g., beads, consisting essentially of polymericresin. Alternatively, the grinding media can comprise particlescomprising a core having a coating of the polymeric resin adheredthereon.

In general, polymeric resins suitable for use herein are chemically andphysically inert, substantially free of metals, solvent and monomers,and of sufficient hardness and friability to enable them to avoid beingchipped or crushed during grinding. Suitable polymeric resins includecrosslinked polystyrenes, such as polystyrene crosslinked withdivinylbenzene, styrene copolymers, polycarbonates, polyacetals, such asDelrin™, vinyl chloride polymers and copolymers, polyurethanes,polyamides, poly(tetrafluoroethylenes), e.g., Teflon™, and otherfluoropolymers, high density polyethylenes, polypropylenes, celluloseethers and esters such as cellulose acetate, polyhydroxymethacrylate,polyhydroxyethyl acrylate, silicone containing polymers such aspolysiloxanes and the like. The polymer can be biodegradable. Exemplarybiodegradable polymers include poly(lactides), poly(glycolide)copolymers of lactides and glycolide, polyanhydrides, poly(hydroxyethylmethacylate), poly(imino carbonates), poly(N-acylhydroxyproline)esters,poly(N-palmitoyl hydroxyproline) esters, ethylene-vinyl acetatecopolymers, poly(orthoesters), poly(caprolactones), andpoly(phosphazenes). In the case of biodegradable polymers, contaminationfrom the media itself advantageously can metabolize in vivo intobiologically acceptable products which can be eliminated from the body.

The polymeric resin can have a density from 0.8 to 3.0 g/cm3. Higherdensity resins are preferred inasmuch as it is believed that theseprovide more efficient particle size reduction.

The media can range in size from about 0.1 to 3 mm. For fine grinding,the particles preferably are from 0.2 to 2 mm, more preferably, 0.25 to1 mm in size.

In a particularly preferred method, a therapeutic or diagnostic agent isprepared in the form of submicron particles by grinding the agent in thepresence of a grinding media having a mean particle size of less thanabout 75 microns.

The core material of the grinding media preferably can be selected frommaterials known to be useful as grinding media when fabricated asspheres or particles. Suitable core materials include zirconium oxides(such as 95% zirconium oxide stabilized with magnesia or yttrium),zirconium silicate, glass, stainless steel, titania, alumina, ferriteand the like. Preferred core materials have a density greater than about2.5 g/cm3. The selection of high density core materials is believed tofacilitate efficient particle size reduction.

Useful thicknesses of the polymer coating on the core are believed torange from about 1 to about 500 microns, although other thicknessesoutside this range may be useful in some applications. The thickness ofthe polymer coating preferably is less than the diameter of the core.

The cores can be coated with the polymeric resin by techniques known inthe art. Suitable techniques include spray coating, fluidized bedcoating, and melt coating. Adhesion promoting or tie layers canoptionally be provided to improve the adhesion between the core materialand the resin coating. The adhesion of the polymer coating to the corematerial can be enhanced by treating the core material to adhesionpromoting procedures, such as roughening of the core surface, coronadischarge treatment, and the like.

Continuous Grinding

In a preferred grinding process, the particles are made continuouslyrather than in a batch mode. The continuous method comprises the stepsof continuously introducing the therapeutic or diagnostic agent andrigid grinding media into a milling chamber, contacting the agent withthe grinding media while in the chamber to reduce the particle size ofthe agent, continuously removing the agent and the grinding media fromthe milling chamber, and thereafter separating the agent from thegrinding media.

The therapeutic or diagnostic agent and the grinding media arecontinuously removed from the milling chamber. Thereafter, the grindingmedia is separated from the milled particulate agent (in either a dry orliquid dispersion form) using conventional separation techniques, in asecondary process such as by simple filtration, sieving through a meshfilter or screen, and the like. Other separation techniques such ascentrifugation may also be employed.

In a preferred embodiment, the agent and grinding media are recirculatedthrough the milling chamber. Examples of suitable means to effect suchrecirculation include conventional pumps such as peristaltic pumps,diaphragm pumps, piston pumps, centrifugal pumps and other positivedisplacement pumps which do not use sufficiently close tolerances todamage the grinding media. Peristaltic pumps are generally preferred.

Another variation of the continuous process includes the use of mixedmedia sizes. For example, larger media may be employed in a conventionalmanner where such media is restricted to the milling chamber. Smallergrinding media may be continuously recirculated through the system andpermitted to pass through the agitated bed of larger grinding media. Inthis embodiment, the smaller media is preferably between about 1 and 300mm in mean particle size and the larger grinding media is between about300 and 1000 mm in mean particle size.

Precipitation Method

Another method of forming the desired nanoparticle dispersion is bymicroprecipitation. This is a method of preparing stable dispersions oftherapeutic and diagnostic agents in the presence of a surface modifyingand colloid stability enhancing surface active agent free of trace ofany toxic solvents or solubilized heavy metal impurities by thefollowing procedural steps:

1. Dissolving the therapeutic or diagnostic agent in aqueous base withstirring,

2. Adding above #1 formulation with stirring to a surface activesurfactant (or surface modifiers) solution to form a clear solution, and

3. Neutralizing above formulation #2 with stirring with an appropriateacid solution. The procedure can be followed by:

4. Removal of formed salt by dialysis or diafiltration and

5. Concentration of dispersion by conventional means.

This microprecipitation process produces dispersion of therapeutic ordiagnostic agents with Z-average particle diameter less than 400 nm (asmeasured by photon correlation spectroscopy) that are stable in particlesize upon keeping under room temperature or refrigerated conditions.Such dispersions also demonstrate limited particle size growth uponautoclave-decontamination conditions used for standard blood-poolpharmaceutical agents.

Step 3 can be carried out in semicontinuous, continuous batch, orcontinuous methods at constant flow rates of the reacting components incomputer controlled reactors or in tubular reactors where reaction pHcan be kept constant using pH-stat systems. Advantages of suchmodifications are that they provide cheaper manufacturing procedures forlarge-scale production of nanoparticulate dispersion systems.

Additional surface modifier may be added to the dispersion afterprecipitation. Thereafter, the dispersion can be mixed, e.g., by shakingvigorously. Optionally, the dispersion can be subjected to a sonicationstep, e.g., using an ultrasonic power supply. For example, thedispersion can be subjected to ultrasonic energy having a frequency of20-80 kHz for a time of about 1 to 120 seconds.

In a preferred embodiment, the above procedure is followed with step 4which comprises removing the formed salts by diafiltration or dialysis.This is done in the case of dialysis by standard dialysis equipment andby diafiltration using standard diafiltration equipment known in theart. Preferably, the final step is concentration to a desiredconcentration of the agent dispersion. This is done either bydiafiltration or evaporation using standard equipment known in this art.

An advantage of microprecipitation is that unlike milled dispersion, thefinal product is free of heavy metal contaminants arising from themilling media that must be removed due to their toxicity before productis formulated.

A further advantage of the microprecipitation method is that unlikesolvent precipitation, the final product is free of any trace of tracesolvents that may be toxic and must be removed by expensive treatmentsprior to final product formulation.

In another preferred embodiment of the microprecipitation process, acrystal growth modifier is used. A crystal growth modifier is defined asa compound that in the co-precipitation process incorporates into thecrystal structure of the microprecipitated crystals of thepharmaceutical agent, thereby hindering growth or enlargement of themicrocrystalline precipitate, by the so called Ostwald ripening process.A crystal growth modifier (or a CGM) is a chemical that is at least 75%identical in chemical structure to the pharmaceutical agent. By“identical” is meant that the structures are identical atom for atom andtheir connectivity. Structural identity is characterized as having 75%of the chemical structure, on a molecular weight basis, identical to thetherapeutic or diagnostic agent. The remaining 25% of the structure maybe absent or replaced by different chemical structure in the CGM. Thecrystal growth modifier is dissolved in step #1 with the therapeutic ordiagnostic agent

Particle Size

As used herein, particle size refers to a number average particle sizeas measured by conventional particle size measuring techniques wellknown to those skilled in the art, such as sedimentation field flowfractionation, photon correlation spectroscopy, or disk centrifugation.When photon correlation spectroscopy (PCS) is used as the method ofparticle sizing the average particle diameter is the Z-average particlediameter known to those skilled in the art. By “an effective averageparticle size of less than about 1000 nm” it is meant that at least 90%of the particles have a weight average particle size of less than about1000 nm when measured by the above-noted techniques. In preferredembodiments, the effective average particle size is less than about 400nm and more preferrably less than about 300 nm. In some embodiments, aneffective average particle size of less than about 100 nm has beenachieved. With reference to the effective average particle size, it ispreferred that at least 95% and, more preferably, at least 99% of theparticles have a particle size less than the effective average, e.g.,1000 nm. In particularly preferred embodiments essentially all of theparticles have a size less than 1000 nm. In some embodiments,essentially all of the particles have a size less than 400 nm.

Ratios

The relative amount of therapeutic or diagnostic agent and surfacemodifier can vary widely and the optimal amount of the surface modifiercan depend, for example, upon the particular therapeutic or diagnosticagent and surface modifier selected, the critical micelle concentrationof the surface modifier if it forms micelles, the hydrophilic lipophilicbalance (HLB) of the stabilizer, the melting point of the stabilizer,its water solubility, the surface tension of water solutions of thestabilizer, etc. The surface modifier preferably is present in an amountof about 0.1-10 mg per square meter surface area of the therapeutic ordiagnostic agent. The surface modifier can be present in an amount of0.1-90%, preferably 20-60% by weight based on the total weight of thedry particle.

Diagnosis

A method for diagnostic imaging for use in medical procedures inaccordance with this invention comprises administering to the body of atest subject in need of a diagnostic image an effective contrastproducing amount of the diagnostic image contrast composition. Inaddition to human patients, the test subject can include mammalianspecies such as rabbits, dogs, cats, monkeys, sheep, pigs, horses,bovine animals and the like. Thereafter, at least a portion of the bodycontaining the administered contrast agent is exposed to x-rays or amagnetic field to produce an x-ray or magnetic resonance image patterncorresponding to the presence of the contrast agent. The image patterncan then be visualized.

Any x-ray visualization technique, preferably, a high contrast techniquesuch as computed tomography, can be applied in a conventional manner.Alternatively, the image pattern can be observed directly on an x-raysensitive phosphor screen-silver halide photographic film combination orby use of a storage phosphor screen.

Visualization with a magnetic resonance imaging system can beaccomplished with commercially available magnetic imaging systems suchas a General Electric 1.5 T Sigma imaging system [1H resonant frequency63.9 megahertz (MHz)]. Commercially available magnetic resonance imagingsystems are typically characterized by the magnetic field strength used,with a field strength of 2.0 Tesla as the current maximum and 0.2 Teslaas the current minimum. For a given field strength, each detectednucleus has a characteristic frequency. For example, at a field strengthof 1.0 Tesla, the resonance frequency for hydrogen is 42.57

10 MHz; for phosphorus-31 it is 17.24 MHz; and for sodium23 it is 11.26Mhz.

A contrast effective amount of the diagnostic agent containingcomposition is that amount necessary to provide tissue visualizationwith, for example, magnetic resonance imaging or x-ray imaging. Meansfor determining a contrast effective amount in a particular subject willdepend, as is well known in the art, on the nature of the magneticallyreactive material used, the mass of the subject being imaged, thesensitivity of the magnetic resonance or x-ray imaging system and thelike.

After administration of the compositions, the subject mammal ismaintained for a time period sufficient for the administeredcompositions to be distributed throughout the subject and enter thetissues of the mammal. Typically, a sufficient time period is from about20 minutes to about 90 minutes and, preferably from about 20 minutes toabout 60 minutes. The following examples are presented for a furtherunderstanding of the invention.

EXAMPLE 1 Using the Therapeutic Agent Beclomethasone

Materials. Beclomethasone diproprionate (BDP) and polyvinyl alcohol(PVA) were obtained from Sigma Chemical Co. (St. Louis, Mo.) and used asreceived. All other chemicals were analytical/reagent grade or better.

Nanoparticle Preparation and Characterization. Nanoparticles wereprepared by media milling a suspension of 5% beclomethasonediproprionate in an aqueous solutions of PVA. Thus, the PVA was thesurface modifier. The resulting particle size distribution wasdetermined by dynamic light scattering. The particle size distributionwas periodically monitored throughout the course of the study.

Nebulization. A gas cylinder of compressed air was used as the source,which was equipped with a pressure regulator. Oxygen connecting tubingjoined from the regulator to the Puritan-Bennet Raindrop nebulizer(Lenexa, Kans.). One exit port of the T-connector of the nebulizer wasblocked with a #2 rubber stopper. The other exit port was fitted withTygon tubing (½″ id). This in turn led initially to a calibrated flowmeter from which the flow rate was set before each experiment. Aftercalibration, the gas flow was stopped by shutting off the main cylindervalve. The flow meter was removed, and the nebulizer was connected to aY-tube with 24/40 joints by tubing (½″ id, 6″ length). The Y-tube wasconnected to the cascade impactor (Andersen Mark I, Andersen SamplersInd. Atlanta, Ga.) by a constructed stainless steel adapter consistingof a tapered side that fit within the 24/40 ground glass joint and acylindrical section with rubber o-ring gasket that fit into the top ofthe cascade impactor. The air flow rate through the impactor was drawnby a vacuum pump and regulated by a calibrated flow meter to therecommended 28.3 L/min.

Preliminary studies indicated that pressures between 20 and 40 psig hadlittle effect on either the performance of the nebulizer or theresulting aerosol size distribution. Thus, the pressure was keptconstant at 40 psig. Studies of the effect of flow rate on nebulizerperformance and aerosol size distribution were also conducted. As theflow rate was decreased from 5 to 2 L/min, aerosol particles hadprogressively larger mean aerodynamic diameter. At a flow rate 8 L/min,there was excessive foaming. Thus, all studies were conducted at a flowrate of 6 L/min.

Suspension and Nanoparticle Nebulization. Formulations for nebulizationconsisted of a 0.2% beclomethasone diproprionate dispersions with PVA.The nebulizers contained either a volume of 2 mL or 6 mL. Twoconcentrations of PVA were used which were prepared by diluting theoriginal 5% (w/v) nanoparticle dispersion with a PVA solution having thesame PVA concentration as the original dispersion concentration or withwater. The nebulizer was filled, and aliquots of the solution were takenfor subsequent determination of drug concentration. The weight was alsodetermined. The nebulization process was initiated by opening the valveon the main gas cylinder, and the length of time until foaming orsputtering of the nebulizer was determined, and additional aliquots weretaken for analysis. The fraction of mass exiting the nebulizer wascalculated from the weight difference of the nebulizer before and afternebulization. This was coupled with the time required for nebulizationof the dispersion to yield the mass output rate in terms of themilliliters of dispersion nebulized/unit time and the nebulizer outputin terms of the volume of dispersion nebulized/liter of air weredetermined.

Aliquots taken from the nebulizer were diluted with 50% (v/v) ethanol inwater, and the absorbance determined at 240 nm. With measurement of theabsorbance of appropriate standards, the concentration of BDP wascalculated. From the masses of the nebulizer before and afternebulization and the BDP concentrations, the fraction of BDP remainingin the nebulizer was calculated. The mass of BDP collected on thecascade impactor and the aerosol particle size distribution wasdetermined by extracting the impactor stages with 10 mL of theethanol/water solution. Aliquots were taken and the absorbances andsubsequent concentration were determined. The mass median aerodynamicdiameter and geometric standard deviation of the particle distributionwas obtained by plotting the cumulative mass on the stages of theimpactor as a function of the log of the cut-off diameter. With thecumulative mass determined from the cascade impactor and the initialamount of BDP placed in the nebulizer, the fraction of BDP reaching theimpactor was calculated.

To assess the fractionation of the dispersion, the nanoparticles andsuspensions were diluted with PVA solutions containing 0.1% sodiumfluorescein. Nebulization was conducted as described above. Sincefluorescein has significant absorbance at both 490 and 240 nm while BDPhas absorbance only at 240 nm, the absorbance of the diluted aliquotswas determined at these two wavelengths. The concentration offluorescein was determined from the absorbance at 490 nm and themeasured absorptivity. In determining the concentrations of BDP, thecontribution from the absorbance of fluorescein at 240 nm was subtractedbased on the absorbance determined at 490 and the correction for thedifferences in the absorptivity at these two wavelength.

Scanning Electron Microscopy. SEM was performed on nanoparticles afternebulization. Two dispersions were prepared containing 0.1 and 2.5%surfactant. These were placed in the nebulizer and 2 cm rectangularglass microscope slides were placed on every stage of the impactor. Theglass slides were removed and sputtered 5 with platinum. Micrographswere obtained with a JEOL 840-1 ElectroScan Environmental ESEM (Peabody,Mass.).

RESULTS

Nanoparticles of beclomethasone diproprionate in 2.5% polyvinyl alcoholhad a particle size distribution of 0.26±0.13 mm. This size remainedconstant throughout the course of the study; neither was there anyevidence of chemical instability. In addition, particle size of thediluted dispersions remained constant for at least the duration of theexperiment.

For nebulization, four formulations were tested. These are listed inTable I. The first was a suspension of raw drug substance BDP in 2.5%surfactant with a volume of 2 mL. The second was composed of adispersion of nanoparticles thereby allowing direct comparison to thesuspension formulation. The third was also a colloidal dispersin, butthe surfactant concentration was smaller at 0.1%. The fourth was similarto the third but contained a larger volume of 6 mL.

In Table II, the results from the nebulization of the four formulationswere given. The second column provides the mass output rate which wasthe rate at which the total mass of the dispersion exists the nebulizer.Formulations I and II are similar as were formulations III and IV. Thedifference between these two sets of formulations is that I and II had asurfactant concentration of 2.5%, whereas III and IV had a surfactantconcentration of 0.1%.

The third column reflects the total mass fraction of dispersionremaining in the nebulizer. The fraction of mass remaining was between0.27 and 0.69 indicating considerable amount of material remained in thenebulizer. In addition, formulations I, II and III were similar, butformulation IV had a significantly lower mass fraction remaining in thenebulizer. Formulation IV is distinct from the others in that itcontained an initial volume of 6 mL.

In the next column, the fraction of BDP remaining in the nebulizer isgiven. These fractions ranged from 0.29 to 0.89. In comparing thefractions remaining, formulation L which contained the suspension, hadabout 90% of BDP remain in the nebulizer. In contrast, formulation IIIwhich contained 0.1% surfactant, had a significantly lower fraction ofBDP remain in the nebulizer. An even more dramatic drop in fractionremaining was observed with formulation IV which had a low surfactantconcentration as well as a larger volume.

It is also noteworthy to compare the fraction of BDP remaining relativeto the fraction of total mass remaining in the nebulizer. Withformulation I, there was a significantly greater fraction of BDPrelative to the total mass remaining. Numerically this is also true forformulation II: however, there was more variability in thesemeasurements which had no statistical difference in the fractionsremaining. In formulations III and IV, there was no difference.

The fraction of BDP reaching the nebulizer is also given in Table II. Itis seen that only about 7% of the BDP presented as a suspension or rawdrug substance reaches the impactor. In comparison, the use ofnanoparticles led to a significantly higher fraction reaching theimpactor. These ranged from 0.17 to over 0.34. In formulations II andIII which contained 2 mL of dispersion, about 18% of BDP reached theimpactor. In the large volume formulation IV, almost 35% of BDP reachedthe impactor.

Finally, it is evident that the amount of BDP that was originally placedin the nebulizer should equal the amount of BDP remaining in thenebulizer added to the amount of BDP on the impactor. Expressing themass balance in terms of fractions, the fraction of BDP remaining in thenebulizer plus the fraction of BDP on the impactor should equal unity.As can be deduced from the fractions given in Table II, this was onlythe case with formulation II. In other cases, there was a net loss ofBDP. In particular, for formulation III, only 80% of BDP was accountedfor, and in formulation IV, the percent accounted for dropped to about60%.

It is evident when the fraction of BDP collected on the impactor stageis plotted as a function of the cut-off diameter of the stage thatsuspensions of raw drug substance have a distribution of particles witha larger size and its distribution is more polydisperse. Thenanoparticles have particles size distributions with 80% of theparticles being less than 2.5 mm.

In Table III, the results from the fluorescein study are given. Incomparing the mass exited, both formulations gave similar results ofabout 0.75. There was also no significant difference between thefractions of BDP and fluorescein remaining in the nebulizer. For thesuspension, the fraction of BDP and fluorescein remaining were 88 and89%, respectively. For the nanoparticles, the percents were 81 and 85which are not statistically different from each other. In addition,there was no statistical difference in the fractions of BDP andfluorescein remaining in the nebulizer between formulations I and II.However, the fractions of BDP and fluorescein remaining aresignificantly greater than the fraction of total mass remaining for thesuspension and nanoparticle formulations.

The fractions of BDP reaching the impactor were different between thetwo formulations. For the suspension, the fraction of fluoresceincollected on the impactor was almost twice as high as the fraction ofBDP. For the nanoparticles, the fraction of fluorescein was similar tothat found with suspensions. The fraction of BDP collected on theimpactor was much higher than observed with suspensions, but slightlyless than that observed with fluorescein.

The final study was an examination of the particles after beingsubjected to the process of nebulization. Scanning electron microscopywas conducted of the nanoparticles deposited on the sixth stage of theimpactor for the 2.5 and 0.1% nanoparticles.

TABLE I Formulation Components Formulation Form [Surfactant] Volume (mL)I Suspension 2.5% 1.85 II Nanoparticle 2.5% 1.85 Dispersion IIINanoparticle 0.1% 1.85 Dispersion IV Nanoparticle 0.1% 5.85 DispersionFormulation “I” is a comparative formulation not using nanoparticles.

TABLE II Comparison of Nebulization Output Parameters as a Function ofFormulate Effect of Nebulization Process on Resulting AerosolProduction. Results are expressed as the mean + standard deviation, n =3. Mass BDP Formu- Mass Output Fraction BDP Fraction Fraction lationRate (mg/sec) Remain. Remain Remain I 2.73 ± 0.5  0.69 ± 0.036  0.89 ±0.013 0.082 ± 0.012 II 2.61 ± 0.14 0.51 ± 0.15  0.768 ± 0.23  0.184 ±0.47  III 4.99 ± 0.31 0.67 ± 0.006 0.618 ± 0.025 0.174 ± 0.019 IV 4.35 ±0.65 0.27 ± 0.015 0.289 ± 0.039 0.345 ± 0.15 

TABLE III Comparison of Nebulization of Nanoparticle Dispersions andSuspensions of BDP Containing a Solution of Fluorescein Mass BDPFluorescein BDP Fluorescein Fraction Fraction Fraction Fraction onFraction On Formulation Remaining Remaining Remaining Impactor ImpactorSuspension 0.76 ± 0.06 0.88 ± 0.046 0.89 ± 0.13  0.067 ± 0.02 0.122 ±0.033 Nanoparticles 0.74 ± 0.17 0.81 ± 0.088 0.85 ± 0.065  0.11 ± 0.0160.143 ± 0.020

EXAMPLE 2 Using a Contrast Agent

In this example, a suspension of WIN 68209 (30%) in aqueous F108surfactant (6%) was prepared by conventional roller milling techniques(ar mill, zirconium silicate beads, 7 days milling time). The meanparticle size of the resultant distribution was 196 μm. The formulationwas administered to an anesthetized rabbit as follows: Several mL offormulation was placed in an ultrasonic nebulizer (DeVilbiss AeroSonic™)which was connected in-line with a mechanical ventilator, terminating ina suitable endotracheal tube. The rabbit was then intubated andadministered the nebulized formulation for several minutes. Subsequentcomputed tomography (CT) scans of the rabbit's pulmonary region showedthe presence of radiopaque contrast agent in the region.

The invention has been described with particular reference to preferredembodiments thereof, but it will be understood that variations andmodifications can be effected within the spirit and scope of theinvention.

1-9. (canceled)
 10. A pharmaceutical composition of an immunosuppressiveagent comprising solid particles of the agent coated with one or moresurface modifiers, wherein the particles have an average effectiveparticle size of less than about 50 nm to less than about 1000 nm. 11.The composition of claim 10, wherein the surface modifier is selectedfrom the group consisting of: anionic surfactants, cationic surfactants,zwitterionic surfactants, nonionic surfactants, surface activebiological modifiers, and combinations thereof.
 12. The composition ofclaim 11, wherein the surface modifier is selected from the groupconsisting of: alkyl sulfonates, alkyl phosphates, triethanolaminestearate, sodium lauryl sulfate, sodium dodecylsulfate, alkylpolyoxyethylene sulfates, sodium alginate, dioctyl sodiumsulfosuccinate, sodium carboxymethylcellulose, calciumcarboxymethylcellulose, benzalkonium chloride, phosphatidylglycerol,polyoxyethylene fatty alcohol ethers, polyoxyethylene sorbitan fattyacid esters, polyoxyethylene fatty acid esters, sorbitan esters,glycerol monostearate, polyethylene glycols, polypropylene glycols,cetyl alcohol, cetostearyl alcohol, polyoxyethylene-polyoxypropylenecopolymers, polaxamines, methylcellulose, hydroxy propylcellulose,hydroxy propylmethylcellulose and noncrystalline cellulose.
 13. Thecomposition of claim 11, wherein the surface modifier is a phospholipid.14. The composition of claim 11, wherein the surface active biologicalmodifier is a protein.
 15. The composition of claim 13, wherein theprotein is casein.
 16. The composition of claim 10, wherein the surfacemodifier comprises a copolymer of oxyethylene and oxypropylene.
 17. Thecomposition of claim 16, wherein the copolymer of oxyethylene andoxypropylene is a block copolymer.
 18. The composition of claim 11,further comprising a pH adjusting agent.
 19. The composition of claim10, wherein the immunosuppressive agent is beclomethasone.